Objective-lens driving apparatus and optical disk apparatus

ABSTRACT

An objective-lens driving apparatus includes permanent magnets on both ends of the movable unit, simultaneously, on the other side of the movable unit parallel to the tracking direction, also a permanent magnet at a position closer to the center of the movable unit. This configuration makes it possible to reduce each moment generated at each of a focusing coil and a tracking coil when an objective lens is displaced.

BACKGROUND OF THE INVENTION

The present invention relates to an objective-lens driving apparatus foruse in an optical disk apparatus for recording information on therecording surface of an optical disk or for reading the informationrecorded thereon.

In an optical disk apparatus for recording information on a disk-shapedrecording medium or for reading and reproducing the information recordedthereon, an objective-lens driving apparatus is an apparatus for drivingan objective lens in the focusing direction (i.e., the direction inwhich the objective lens comes closer to/goes away from the recordingsurface of the optical disk) and in the tracking direction (i.e., theradial direction of the disk). Here, the objective lens light-convergeslight on the optical-disk recording surface. Generally, theobjective-lens driving apparatus incorporates a movable unit with theobjective lens, a supporting member for supporting this movable unit,and a magnetic circuit with a yoke and a permanent magnet. A focusingcoil and a tracking coil are mounted onto the movable unit. Applying adriving current to the focusing coil drives the movable unit in thefocusing direction by an electromagnetic force generated by theinteraction with a magnetic flux from the permanent magnet. Similarly,applying the driving current to the tracking coil drives the movableunit in the tracking direction by an electromagnetic force generated bythe interaction with the magnetic flux from the permanent magnet.

In the objective-lens driving apparatus like this, if the objective lenshas been inclined, an optical aberration occurs, thereby enlarging alight-converged spot. This makes it impossible to correctly record theinformation on the disk, or results in a degradation in the reproducedsignal.

Conventionally, there has been known the optical pick-up unit which wasdevised in order to suppress this inclination of the objective lens(e.g., JP-A-2001-101687). This optical pick-up unit incorporates thetracking coil, the focusing coil, the objective lens, a lens holder, adamper base for supporting the lens holder in a movable manner viaplural suspension wires, the yoke, and the permanent magnet. Moreover,in the optical pick-up unit, the configuration size of the permanentmagnet is set so that electromagnetic forces, which exert themselves onthe tracking coil and/or the focusing coil thereby to cause the opticalaxis of the objective lens to be inclined from its reference axis, willsubstantially cancel out each other.

In the above-described related art, the configuration size of thepermanent magnet is set at a certain value. This setting has canceledout moments generated at the focusing coil and the tracking coil whenthe objective lens is displaced, thereby suppressing the inclination ofthe objective lens. This setting, however, imposes the restrictions onthe sizes of the permanent magnet, the focusing coil, and the trackingcoil. As a consequence, the design's degree-of-freedom has been limited,and there has been acquired only effect that is not necessarilysufficient in an aspect of the apparatus's downsizing.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide an objective-lensdriving apparatus and an optical disk apparatus where, even when theobjective lens is displaced, the inclination of the objective lensbecome small, and the dependency on the size of magnetic circuit becomelow.

In order to accomplish the above-described object, in the presentinvention, there is provided an objective-lens driving apparatus thatincorporates the following configuration components: an objective lensfor light-converging light on the recording surface of an optical disk,a lens holder for holding the objective lens, a focusing coil and atracking coil mounted onto the lens holder, plural supporting membersfor supporting a movable unit, which incorporates the lens holder, in amovable manner in the focusing direction and the tracking direction withrespect to a fixed unit, a yoke member having a magnetic substance, andplural permanent magnets located in parallel to the tracking directionand on both ends of the movable unit. Moreover, in the objective-lensdriving apparatus, on one side of the movable unit parallel to thetracking direction, the permanent magnets are located on both ends ofthe movable unit. Simultaneously, on the other side of the movable unitparallel to the tracking direction, the permanent magnets is located ata position closer to the center of the movable unit.

With the permanent magnets, the focusing coil and the tracking coilarranged as described above, this configuration makes it possible toreduce each moment generated at each of the focusing coil and thetracking coil when the objective lens is displaced. Accordingly, itbecomes possible to implement the objective-lens driving apparatus and,eventually, the optical disk apparatus where the inclination of theobjective lens becomes small.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram for illustrating an embodiment of the objective-lensdriving apparatus according to the present invention;

FIG. 2 is a top view for illustrating a major portion in FIG. 1;

FIG. 3 is a top view for illustrating a magnetic-flux densitydistribution in the embodiment in FIG. 1;

FIG. 4 is a side view for illustrating the magnetic-flux densitydistribution in the embodiment in FIG. 1;

FIG. 5 is a diagram for explaining a force that exerts itself on afocusing coil in the embodiment in FIG. 1;

FIG. 6A and FIG. 6B are diagrams for explaining a force that exertsitself on a tracking coil in the embodiment in FIG. 1;

FIG. 7 is a diagram for illustrating another embodiment of theobjective-lens driving apparatus according to the present invention;

FIG. 8 is a top view for illustrating a magnetic-flux densitydistribution in the embodiment in FIG. 7; and

FIG. 9 is a diagram for illustrating still another embodiment of theobjective-lens driving apparatus according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, the explanation will be given belowconcerning embodiments of the present invention. The optical diskapparatus according to the present invention drives the objective lensby the objective-lens driving apparatus so as to light-converge light onthe recording surface of the optical disk, thereby performing thereproduction of information.

FIG. 1 is an exploded perspective view for illustrating theconfiguration of an embodiment of the objective-lens driving apparatus.In FIG. 1, the x-axis direction is the tangent direction of anot-illustrated disk. The y-axis direction is the tracking direction,i.e., the radial direction of the disk. The z-axis direction is thefocusing direction, i.e., the optical-axis direction of an objectivelens 1.

A focusing coil 3, i.e., a driving coil, is wound around a lens holder 2for holding the objective lens 1. Also, four tracking coils 4 a, 4 b, 4c and 4 d are mounted onto the lens holder 2. One ends of wire-likesupporting members 6 having electrical conductivity are fixed to a fixedunit 7, and the other ends thereof are fixed to the side of the lensholder 2.

Here, the objective lens 1, the lens holder 2, the focusing coil 3 andthe tracking coils 4 a to 4 d turn out to become a movable unit.

Permanent magnets 11 a, 11 b, and 11 c whose magnetization directionsbecome identical to the x-axis direction in the drawing are mounted ontoand fixed to outer yokes 9, i.e., yoke members including a magneticsubstance, on both ends of the movable unit parallel to the trackingdirection.

From bottom surfaces of the outer yokes 9, inner yokes 10, i.e., yokemembers including a magnetic substance similarly, are located such thatthe inner yokes 10 are positioned at the inner side of the focusing coil3. This configuration forms a magnetic circuit where magnetic fluxesfrom the permanent magnets 11 a to 11 c pass through to the inner yokes10 and the outer yokes 9.

Here, on one side of the movable unit parallel to the tracking directionwhich is the y-axis direction in the drawing, the permanent magnets 11 aand 11 b are arranged apart on both ends of the movable unit.Simultaneously, on the other side of the movable unit parallel to thetracking direction, the permanent magnet 11 c is arranged at the centerof the movable unit.

FIG. 2 is a top view of the objective-lens driving apparatus illustratedin FIG. 1. Here, in order to make the drawing easy to see, there areillustrated only the focusing coil 3, the tracking coils 4 a to 4 d, thepermanent magnets 11 a to 11 c, the outer yokes 9 and the inner yokes10. As illustrated in FIG. 2, the tracking coils 4 a and 4 b are locatedat positions closer to the center of the movable unit with respect tothe permanent magnets 11 a and 11 b arranged apart in the trackingdirection. The tracking coils 4 c and 4 d are arranged at the outer sideof the movable unit with respect to the permanent magnet 11 c. Namely,the permanent magnets 11 a and 11 b confront the coil-wound portionspositioned at the outer sides of the tracking coils 4 a and 4 b, and thepermanent magnet 11 c confronts the coil-wound portion positioned at theinner side of the tracking coils 4 c and 4 d.

In the objective-lens driving apparatus configured as described above,the magnetic-flux density distribution turns out to become one asillustrated in a top view in FIG. 3 and a side view in FIG. 4. Eachmagnetic-flux density is the largest at the central portion of eachpermanent magnet, and becomes smaller and smaller at a more peripheralportion of each permanent magnet. Accordingly, as illustrated in FIG. 3,the distribution turns out to be as follows: on the side of thepermanent magnets 11 a and 11 b, the magnetic-flux density is large onboth ends of the focusing coil 3. On the side of the permanent magnet 11c, the magnetic-flux density is large at the center of the focusing coil3.

Concerning the polarities of the permanent magnets 11 a to 11 c, thepolarities on the closer sides to the focusing coil 3 are set to be theN poles, and the polarities on the sides of the outer yokes 9 are set tobe the S poles. Then, as illustrated in FIG. 5, causing an electriccurrent 51 to flow through the focusing coil 3 generates a z-directionforce at the focusing coil 3, thereby driving the movable unit in thez-axis direction which is the focusing direction. Also, as illustratedin FIG. 6A and FIG. 6B, causing an electric current 52 to flow throughthe tracking coils 4 a to 4 d generates y-direction forces at thetracking coils 4 a to 4 d, thereby driving the movable unit in they-axis direction which is the tracking direction.

Here, assuming that the displacement amount in the tracking direction isequal to Δy, and that the displacement amount in the focusing directionis equal to Δz. Then, as illustrated in FIG. 5, the side of the focusingcoil 3 confronting the permanent magnets 11 a and 11 b goes away fromthe permanent magnet 11 a, and confronts the permanent magnet 11 bentirely. As a result, a force 61 generated at the portion confrontingthe permanent magnet 11 a becomes smaller, and a force 62 generated atthe portion confronting the permanent magnet 11 b becomes larger. Thisgenerates a moment 91 by the center of the movable unit around the xaxis. Meanwhile, on the side of the focusing coil 3 confronting thepermanent magnet 11 c, the magnetic-flux density distribution from thepermanent magnet 11 c does not change, and the center of the movableunit is displaced by Δy. This, based on a force 63 in the focusingdirection and the distance Δy with the center of the movable unit,generates a moment 92 by the center of the movable unit around the xaxis. At this time, the moment 91 and the moment 92 become opposite toeach other in their directions. This condition reduces a resultantmoment that exerts itself on the focusing coil 3 as a whole. Namely, itbecomes possible to reduce the force that causes the movable unit to beinclined.

Also, in the tracking coils 4 a to 4 d, as illustrated in FIG. 6A andFIG. 6B, in addition to the driving forces 71, 74, 77, and 80 in thetracking direction, forces 72, 75, 78, and 81 are generated at theupper-side portions of the tracking coils 4 a to 4 d, and forces 73, 76,79, and 82 are generated at the lower-side portions thereof. At thistime, the movable unit is displaced by Δz in the focusing direction. Asa result of this, the forces generated at the lower-side portions of thetracking coils 4 a to 4 d become larger than the forces generated at theupper-side portions thereof. This generates a moment 101 and a moment102 by the center of the movable unit around the x axis. Here, however,the portions confronting the permanent magnets 11 a and 11 b differ fromthe portion confronting the permanent magnet 11 c in that the portionsare positioned at the outer sides of the tracking coils 4 a and 4 b andthe portion is positioned at the inner side of the tracking coils 4 cand 4 d. This makes the generated forces opposite to each other in theirdirections. Accordingly, the moment 101 generated at the tracking coils4 a and 4 b and the moment 102 generated at the tracking coils 4 c and 4d become opposite to each other in their directions. This conditionreduces a resultant moment that exerts itself on the tracking coils 4 ato 4 d as a whole. Namely, it becomes possible to reduce the forces thatcause the movable unit to be inclined.

As having been described so far, in the present embodiment, on one sideof the movable unit parallel to the tracking direction, the permanentmagnets 11 a and 11 b are arranged apart on both ends of the movableunit. Simultaneously, on the other side of the movable unit parallel tothe tracking direction, the permanent magnet 11 c is arranged at thecenter of the movable unit. This configuration makes it possible notonly to reduce the moments generated at the focusing coil 3, but also toreduce the moments generated at the tracking coils 4 a to 4 d.Consequently, it becomes possible to implement the objective-lensdriving apparatus and, eventually, the optical disk apparatus where theinclination of the objective lens is found to be small.

Next, referring to FIG. 7 and FIG. 8, the explanation will be givenbelow concerning another embodiment of the present invention. FIG. 7 isan exploded perspective view for illustrating the configuration of theobjective-lens driving apparatus in the present embodiment. FIG. 8 is atop view for illustrating its major portion and its magnetic-fluxdensity distribution.

Two focusing coils 33 a and 33 b, i.e., driving coils, and four trackingcoils 34 a, 34 b, 34 c and 34 d are mounted onto a lens holder 32 forholding an objective lens 31. One ends of wire-like supporting members36 having electrical conductivity are fixed to a fixed unit 37, and theother ends thereof are fixed to the side of the lens holder 32.

Permanent magnets 41 a, 41 b, 41 c and 41 d whose magnetizationdirections become identical to the x-axis direction in the drawing aremounted onto and fixed to outer yokes 39, i.e., yoke members including amagnetic substance, on both ends of the movable unit parallel to thetracking direction.

From bottom surfaces of the outer yokes 39, inner yokes 40, i.e., yokemembers including a magnetic substance similarly, are arranged such thatthe inner yokes 40 are positioned at the inner side of the focusingcoils 33 a and 33 b.

Here, on one side of the movable unit parallel to the tracking directionwhich is the y-axis direction in the drawing, the permanent magnets 41 aand 41 b are arranged apart on both ends of the movable unit.Simultaneously, on the other side of the movable unit parallel to thetracking direction, the permanent magnets 41 c and 41 d are arranged atpositions closer to the center of the movable unit.

As illustrated in FIG. 8, the tracking coils 34 a and 34 b are arrangedat positions closer to the center of the movable unit with respect tothe permanent magnets 41 a and 41 b arranged apart on both ends of themovable unit. The tracking coils 34 c and 34 d are arranged at the outerside of the movable unit with respect to the permanent magnets 41 c and41 d. Namely, the permanent magnets 41 a and 41 b confront thecoil-wound portions positioned at the outer sides of the tracking coils34 a and 34 b, and the permanent magnets 41 c and 41 d confront thecoil-wound portions positioned at the inner sides of the tracking coils34 c and 34 d.

The magnetic-flux density distribution turns out to be as follows: onthe side of the permanent magnets 41 a and 41 b, the magnetic-fluxdensity is large on both ends of the movable unit. On the side of thepermanent magnets 41 c and 41 d, the magnetic-flux density exhibits twopeaks at positions closer to the center of the movable unit.

The present embodiment differs from the first embodiment in that thefocusing coil is divided into the two units, and that there are providedthe four permanent magnets. However, on one side of the movable unitparallel to the tracking direction, the permanent magnets 41 a and 41 bare arranged apart on both ends of the movable unit. Simultaneously, onthe other side of the movable unit parallel to the tracking direction,the permanent magnets 41 c and 41 d are arranged at the positions closerto the center of the movable unit than both ends thereof. Thisconfiguration allows the implementation of basically the same effectconcerning a reduction in moments generated at the focusing coils 33 aand 33 b when the objective lens is displaced, and a reduction inmoments generated at the tracking coils 34 a to 34 d at that time.

Moreover, the two focusing coils 33 a and 33 b are arranged in a mannerof being apart from each other. This configuration allows the creationof a space within the side surface of the movable unit, thereby makingit possible to permit light to pass through the movable unit.Accordingly, it becomes possible to implement the fabrication of athin-type driving apparatus.

Also, the two permanent magnets are each arranged on both ends of themovable unit. This configuration makes it possible to make the size ofthe permanent magnets 41 a and 41 b identical or substantially identicalto the size of the permanent magnets 41 c and 41 d. This, further,allows an effect of facilitating the maintenance of a balance among thedriving forces.

Next, referring to FIG. 9, the explanation will be given belowconcerning still another embodiment of the present invention. FIG. 9 isa top view for illustrating a major portion of the objective-lensdriving apparatus in the present embodiment.

In the present embodiment, each of permanent magnets 111 a, 111 b, 111 cand 111 d is formed as a double-pole-magnetized permanent magnet. Inaddition, each of tracking coils 121 a, 121 b, 121 c and 121 d islocated in a manner of confronting each of boundary portions of thedouble magnetic poles. The other configuration is the same as the one inFIG. 7 and FIG. 8, and thus the explanation thereof will be omittedhere.

The employment of this configuration allows a characteristic that, ineach of the tracking coils 121 a, 121 b, 121 c and 121 d, the portiongenerating a driving force in the tracking direction includes two sides.This characteristic makes it possible to increase the driving force inthe tracking direction, thereby allowing the fabrication of theobjective-lens driving apparatus having a high driving efficiency, i.e.,a small power consumption.

According to the present invention, it becomes possible to provide theobjective-lens driving apparatus and the optical disk apparatus where,even when the objective lens is displaced, the inclination of theobjective lens is small.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. An objective-lens driving apparatus, comprising: an objective lensfor light-converging light on the recording surface of an optical disk,a lens holder for holding said objective lens, a focusing coil andtracking coils mounted onto said lens holder, plural supporting membersfor supporting a movable unit in a movable manner in a focusingdirection and a tracking direction with respect to a fixed unit, saidmovable unit including said lens holder, a yoke member including amagnetic substance, and plural permanent magnets arranged in parallel tosaid tracking direction and at least with respect to both ends of saidmovable unit, wherein, with respect to one side of said movable unitparallel to said tracking direction, said permanent magnets are arrangedwith respect to both ends of said movable unit, and with respect to theother side of said movable unit parallel to said tracking direction, atleast one of said permanent magnets is arranged at a position which isone of close to the center of said movable unit and at the center ofsaid movable unit.
 2. An objective-lens driving apparatus, according toclaim 1, wherein said at least one of said permanent magnets is arrangedat a position close to the center of said movable unit.
 3. Anobjective-lens driving apparatus according to claim 1, wherein saidplural permanent magnets are arranged on said yoke member.
 4. Anobjective-lens driving apparatus, comprising: an objective lens forlight-converging light on the recording surface of an optical disk, alens holder for holding said objective lens, a focusing coil andtracking coils mounted onto said lens holder, plural supporting membersfor supporting a movable unit in a movable manner in a focusingdirection and a tracking direction with respect to a fixed unit, saidmovable unit including said lens holder, a yoke member including amagnetic substance, and plural permanent magnets arranged in parallel tosaid tracking direction and at least with respect to both ends of saidmovable unit, wherein, with respect to one side of said movable unitparallel to said tracking direction, two of said permanent magnets arearranged with respect to both ends of said movable unit, and, withrespect to the other side of said movable unit parallel to said trackingdirection, at least one of said permanent magnets is arranged at thecenter of said movable unit.
 5. An objective-lens driving apparatusaccording to claim 4, wherein said plural permanent magnets are arrangedon said yoke member.
 6. An objective-lens driving apparatus, comprising:an objective lens for light-converging light on the recording surface ofan optical disk, a lens holder for holding said objective lens, afocusing coil and tracking coils mounted onto said lens holder, pluralsupporting members for supporting a movable unit in a movable manner ina focusing direction and a tracking direction with respect to a fixedunit, said movable unit including said lens holder, a yoke memberincluding a magnetic substance, and plural permanent magnets arranged inparallel to said tracking direction and at least with respect to bothends of said movable unit, wherein, with respect to one side of saidmovable unit parallel to said tracking direction, said permanent magnetsare arranged such that a magnetic-flux density therefrom becomes largeron both ends of said focusing coil, and with respect to the other sideof said movable unit parallel to said tracking direction, at least oneof said permanent magnets is located such that a magnetic-flux densitytherefrom will become larger at a position closer to the center of saidfocusing coil.
 7. An objective-lens driving apparatus according to claim6, wherein said plural permanent magnets are arranged on said yokemember.
 8. An objective-lens driving apparatus, comprising: an objectivelens for light-converging light on the recording surface of an opticaldisk, a lens holder for holding said objective lens, a focusing coil andtracking coils mounted onto said lens holder, plural supporting membersfor supporting a movable unit in a movable manner in a focusingdirection and a tracking direction with respect to a fixed unit, saidmovable unit including said lens holder, a yoke member including amagnetic substance, and plural permanent magnets arranged in parallel tosaid tracking direction and at least with respect to both ends of saidmovable unit, wherein, with respect to one side of said movable unitparallel to said tracking direction, said permanent magnets are arrangedin a manner of confronting coil-wound portions positioned at the outersides of said tracking coils, and with respect to the other side of saidmovable unit parallel to said tracking direction, at least one of saidpermanent magnets is arranged in a manner of confronting a coil-woundportion positioned at the inner side of said tracking coils.
 9. Anobjective-lens driving apparatus according to claim 8, wherein saidplural permanent magnets are arranged on said yoke member.
 10. Anoptical disk apparatus for performing the reproduction of informationfrom the recording surface of an optical disk by using an objective-lensdriving apparatus, said objective-lens driving apparatus, comprising: anobjective lens for light-converging light on said recording surface ofsaid optical disk, a lens holder for holding said objective lens, afocusing coil and tracking coils mounted onto said lens holder, pluralsupporting members for supporting a movable unit in a movable manner ina focusing direction and a tracking direction with respect to a fixedunit, said movable unit including said lens holder, a yoke memberincluding a magnetic substance, and plural permanent magnets arranged inparallel to said tracking direction and at least with respect to bothsides of said movable unit, wherein with respect to one side of saidmovable unit parallel to said tracking direction, said permanent magnetsare arranged with respect to both ends of said movable unit, and withrespect to the other side of said movable unit parallel to said trackingdirection, at least one of said permanent magnets is arranged at aposition closer to the center of said movable unit.
 11. Anobjective-lens driving apparatus according to claim 10, wherein saidplural permanent magnets are arranged on said yoke member.
 12. Anoptical disk apparatus for performing the reproduction of informationfrom the recording surface of an optical disk by using an objective-lensdriving apparatus, said objective-lens driving apparatus, comprising: anobjective lens for light-converging light on said recording surface ofsaid optical disk, a lens holder for holding said objective lens, afocusing coil and tracking coils mounted onto said lens holder, pluralsupporting members for supporting a movable unit in a movable manner ina focusing direction and a tracking direction with respect to a fixedunit, said movable unit including said lens holder, a yoke memberincluding a magnetic substance, and plural permanent magnets arranged inparallel to said tracking direction and at least with respect to bothends of said movable unit, wherein, with respect to one side of saidmovable unit parallel to said tracking direction, two of said permanentmagnets are arranged with respect to both ends of said movable unit, andwith respect to the other side of said movable unit parallel to saidtracking direction, at least one of said permanent magnets is arrangedat the center of said movable unit.
 13. An objective-lens drivingapparatus according to claim 12, wherein said plural permanent magnetsare arranged on said yoke member.
 14. An optical disk apparatus forperforming the reproduction of information from the recording surface ofan optical disk by using an objective-lens driving apparatus, saidobjective-lens driving apparatus, comprising: an objective lens forlight-converging light on said recording surface of said optical disk, alens holder for holding said objective lens, a focusing coil andtracking coils mounted onto said lens holder, plural supporting membersfor supporting a movable unit in a movable manner in a focusingdirection and a tracking direction with respect to a fixed unit, saidmovable unit including said lens holder, a yoke member including amagnetic substance, and plural permanent magnets arranged in parallel tosaid tracking direction and at least with respect to both ends of saidmovable unit, wherein, with respect to one side of said movable unitparallel to said tracking direction, said permanent magnets are arrangedsuch that a magnetic-flux density therefrom becomes larger on both endsof said focusing coil, and with respect to the other side of saidmovable unit parallel to said tracking direction, at least one of saidpermanent magnets is arranged such that a magnetic-flux densitytherefrom becomes larger at a position closer to the center of saidfocusing coil.
 15. An objective-lens driving apparatus according toclaim 14, wherein said plural permanent magnets are arranged on saidyoke member.
 16. An optical disk apparatus for performing thereproduction of information from the recording surface of an opticaldisk by using an objective-lens driving apparatus, said objective-lensdriving apparatus, comprising: an objective lens for light-converginglight on said recording surface of said optical disk, a lens holder forholding said objective lens, a focusing coil and tracking coils mountedonto said lens holder, plural supporting members for supporting amovable unit in a movable manner in a focusing direction and a trackingdirection with respect to a fixed unit, said movable unit including saidlens holder, a yoke member including a magnetic substance, and pluralpermanent magnets arranged in parallel to said tracking direction and atleast with respect to both ends of said movable unit, wherein, withrespect to one side of said movable unit parallel to said trackingdirection, said permanent magnets are arranged in a manner ofconfronting coil-wound portions positioned at the outer sides of saidtracking coils, and with respect to the other side of said movable unitparallel to said tracking direction, at least one of said permanentmagnets is arranged in a manner of confronting a coil-wound portionpositioned at the inner side of said tracking coils.
 17. Anobjective-lens driving apparatus according to claim 16, wherein saidplural permanent magnets are arranged on said yoke member.